Shared light pipe for a message indicator and light sensor

ABSTRACT

A shared light pipe is set forth for transmitting light generated by a message waiting LED in a mobile communication device, in one direction, and transmitting ambient or surrounding light, in an opposite direction, to a light sensor for controlling a display backlight of the device. The light pipe includes an elongated first portion having a first end for receiving and transmitting light and external surfaces for reflecting light there through via total internal reflection (TIR), a second portion coextensive with the first portion for outputting light received at the first end and reflected through the first portion, and a second branch coextensive with the first portion for receiving and transmitting light for output at the first end.

FIELD

The following is directed in general to light pipes, and moreparticularly to a shared light pipe for message indicator and lightsensor on a mobile communication device.

BACKGROUND

Mobile communication devices are becoming increasingly popular forbusiness and personal use due to a relatively recent increase in numberof services and features that the devices and mobile infrastructuressupport. Handheld mobile communication devices, sometimes referred to asmobile stations, are essentially portable computers having wirelesscapability, and come in various forms. These include Personal DigitalAssistants (PDAs), cellular phones and smart phones. The user interfacefor such devices typically includes, a keyboard, a message waitingindicator to indicate received voice or email messages, and an LCDdisplay.

The message waiting indicator typically comprises an LED mounted to aprinted circuit board (PCB) within the device and a light pipe(sometimes referred to as a light guide) for transmitting light viaTotal Internal Reflection (TIR) from the LED to the surface of thedevice, so as o be visible to the user. The circuitry within the devicecauses the LED to flash upon receipt of a message, thereby notifying theuser. The design and operation of such circuitry would be well known toa person of skill in the art, and does not form part of the presentspecification.

The LCD display typically includes a backlight control device to controlvariable brightness or to maintain the brightness of the display. Thebacklight control device includes a backlight lamp mounted on the backof an LCD to emit light, a light sensor for measuring intensity of theexternal or surrounding light, and an A/D converter for converting anelectric signal, detected and generated by the light sensor, into adigital signal for controlling the backlight lamp.

It is highly desirable to minimize the size of such mobile communicationdevices for enhanced portability. However, incorporation of the lightsensor consumes valuable real-estate on the surface of the device, andmay detract from the appearance of the device.

SUMMARY

According to an aspect of this specification, a shared light pipe isprovided for transmitting light generated by the internal messagewaiting LED, in one direction, and transmitting ambient or surroundinglight, in an opposite direction, to an internal light sensor forcontrolling the backlight. Unlike the prior art, the shared light pipeas disclosed herein facilitates reduced size of the mobile communicationdevice by minimizing real-estate on the surface of the device and on thePCB because the LED and light sensor can be placed very close together.

Additional aspects and advantages will be apparent to a person ofordinary skill in the art, residing in the details of construction andoperation as more fully hereinafter described and claimed, referencebeing had to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

A detailed description of the preferred embodiment is set forth indetail below, with reference to the following drawings, in which:

FIG. 1 is schematic representation of a message waiting indicator for amobile communication device according to the prior art; and

FIG. 2 is a schematic representation of a shared light pipe for messageindicator and light sensor, according to the preferred embodiment.

DETAILED DESCRIPTION

With reference to FIG. 1, a prior art message waiting indicator is showncomprising a light pipe 1 for transmitting light from a message LED 3 toa viewing surface 2 flush with the surface of a mobile communicationdevice (not shown). The light pipe 1 generally comprises an elongatedtransparent or translucent member having reflection surfaces. As wellknown in the art, when a light ray is directed from the LED 3 into thelight pipe and subtends a surface of the light pipe, if the incidentangle formed by the light ray and the surface is less than a criticalangle, the light is reflected back into the light pipe along atrajectory that defines a reflected angle equal to the incident angleand toward an opposite surface of the guide. Provided the light pipe 1is designed properly and light rays directed into it are directed alongsuitable trajectories, the light pipe facilitates total internalreflection (TIR) of the light and hence passes all of the light to theopposite end 2 of the guide for viewing by a user. As discussed above,circuitry is provided within the device for causing the LED to flashupon receipt of a message, thereby notifying the user. The electroniccircuitry is not shown, but would be well known to a person of skill inthe art.

As discussed above, a light sensor may also be provided for controllingthe display backlight. According to the prior art, such a light sensoris separate from the message indicator and is mounted directly to thesurface of the mobile communication device.

According to the preferred embodiment of FIG. 2, a shared light pipe 5is provided for transmitting light from the message LED 3 to the surface2, as discussed above in connection with FIG. 1. However, the sharedlight pipe 5 contains a pair of branches at a distal portion thereof,opposite the viewing surface, where one branch 9A channels light fromthe LED 3, and the other branch channels light to the internal lightsensor 7.

Preferably, the light pipe as disclosed herein, is molded frompolycarbonate or acrylic, although it can alternatively be selected frombar stock.

In operation, the message light LED 3 is typically flashed according tothe following pattern: 0.5 second on, 3 to 5 seconds off. The lightsensor 7 is read by an internal processor (not shown) when the messageLED 3 is off, thereby avoiding interference between generated and sensedlight within the light pipe 5.

Although not directly relevant to this disclosure, three readings aretypically recorded from light sensor 7 in order to manage thebacklighting function. A self test can also be performed by illuminatingthe LED 3 while taking a measurement at the light sensor 7, therebyconfirming the presence of both the LED 3 and sensor 7. Additionally, ifthe LED 3 has multiple colours then the light sensor 7 can be used toconfirm that as well (a test typically performed during the devicemanufacturing process).

In summary, the shared light pipe set forth herein effectivelyfacilitates reduced size of the mobile communication device byminimizing real-estate on the surface of the device and on the PCB, andalso minimizes the number of light pipes required for message lightdisplay and light sensing.

A person skilled in the art, having read this description of thepreferred embodiment, may conceive of variations and alternativeembodiments. For example, although the preferred embodiment refers toimplementation within a mobile communication device (such as a PDA,cellular phone or smart phone), it is contemplated that the shared lightpipe set forth herein may also be employed to advantage within desktoptelephones, pagers or other communication devices.

All such variations and alternative embodiments are believed to bewithin the ambit of the claims appended hereto.

1. A light pipe for use in a communication device, comprising: anelongated first portion having a first end for receiving andtransmitting light and reflection surfaces for reflecting said lighttherethrough via total internal reflection (TIR); a first branchcoextensive with said first portion for outputting light received atsaid first end and reflected through said first portion so as to bevisible external to said communication device; and a second branchcoextensive with said first portion for transmitting light receivedexternal to said communication device through said first portion foroutput at said first end.
 2. The light pipe of claim 1, wherein saidfirst portion, first branch and second branch are fabricated from one ofeither translucent or transparent material.
 3. The light pipe of claim2, wherein said material is molded from polycarbonate.
 4. The light pipeof claim 2, wherein said material is molded from acrylic.
 5. The lightpipe of claim 2, wherein said material is bar stock.
 6. Apparatus forproviding a visual indication and for measuring light intensityexternally of a communication device, comprising: a Light Emitting Diode(LED) disposed within said device; a light sensor disposed within saiddevice; and a generally Y-shaped light pipe having an elongated firstportion terminating adjacent said LED and light sensor, a first branchcoextensive with said first portion and terminating on a surface of saiddevice for outputting light received from said LED so as to be visibleexternal to said device, and a second branch coextensive with said firstportion and terminating on said surface of said device for transmittinglight received external to said communication device for output to saidlight sensor.
 7. The apparatus of claim 6, wherein said first portion,first branch and second branch are fabricated from one of eithertranslucent or transparent material.
 8. The apparatus of claim 7,wherein said material is molded from polycarbonate.
 9. The apparatus ofclaim 7, wherein said material is molded from acrylic.
 10. The apparatusof claim 7, wherein said material is bar stock.
 11. A method ofoperating a message light and an ambient light sensor opticallyconnected via a shared light pipe, comprising: flashing said messagelight according to a predetermined pattern; and reading an output ofsaid light sensor when said light is not being flashed, thereby avoidinginterference between generated and sensed light within the shared lightpipe.
 12. The method of claim 11, wherein said light is pattern isapproximately 0.5 seconds on, followed by from approximately 3 toapproximately 5 seconds off.
 13. A method of confirming the presence ofboth a message light and an ambient light sensor optically connected viaa shared light pipe, comprising: flashing said message light; andsimultaneously reading an output of said light sensor.